1. Field of the Invention
The present invention relates to a communication control apparatus which is connectable to a data processing apparatus and is typified by a network card device, the data processing apparatus, and a control method therefor.
2. Description of the Related Art
There has been proposed a method using an intelligent network card device which is connectable to a printing apparatus and has desired optional functions for it.
In this case, the printing apparatus main body and the network card device are intelligent both with CPUs. In general, the network card device has a print server function of performing overall control of various print services via a network. The printing apparatus and the network card device communicate with each other via a connection interface to implement a desired service.
As a feature, the network card device communicates with a communication terminal on a network by using the same network address (e.g., IP address) as that of the printing apparatus. This means that a communication terminal on the network recognizes the printing apparatus and the network card device as one communication terminal on the network. The network card device can provide a service such as the print server function as if the service was added to the printing apparatus main body.
The network card device and the printing apparatus use a network protocol such as TCP/IP in communicating with an external apparatus on a network. Recently, the IETF (Internet Engineering Task Force) has proposed IP version 6 (to be referred to as IPv6 hereinafter) as a network layer protocol used in TCP/IP communication. IPv6 expands the IP address space from the currently pervading IP version 4 (to be referred to as IPv4 hereinafter). IPv6 copes with the shortage of global addresses along with rapid expansion of the Internet world.
The IPv6 protocol has a link-local address automatically generated by concatenating an interface identifier generated from an IEEE identifier (MAC address) to a specific network prefix. The IPv6 protocol also has a stateless address generated by concatenating an interface identifier generated from an IEEE identifier (MAC address) to a network prefix advertised from a router. Further, the IPv6 protocol has a stateful address designated from DHCP.
The IPv6 protocol can assign these network addresses to one physical interface. The network address may be added or changed at any time during activation in accordance with manual settings from a user or an advertisement from a router.
When the printing apparatus and the network card device are compatible with the IPv6 protocol, a mechanism which allows them to always use the same network addresses is necessary.
As a conceivable means for this, the printing apparatus notifies the network card device of a new network address by a predetermined means every time the printing apparatus obtains or generates the new network address.
However, when viewed from the printing apparatus, the network card device is not always mounted in the connection interface of the printing apparatus. As the mounted network card device, various types of network card devices exist. For example, a network card device having only the physical layer in the network protocol does not require any network address, and may not have a means for receiving a network address from the printing apparatus.
In the above-described method, the printing apparatus must determine whether any network card device is mounted in the connection interface of the printing apparatus. If a network card device is mounted, the printing apparatus must determine the type of the mounted network card device. Only when the mounted network card device requires a network address, the printing apparatus actually notifies it of a network address.
The network card device is provided as an expansion option of the printing apparatus. Despite this, the printing apparatus recognizes the type of network card device and the like, and operates in accordance with the type. This means that, every time a new network card device is introduced, the printing apparatus must individually deal with it, which is not desirable.
As another conceivable means, the network card device always monitors communication between the printing apparatus and a communication terminal on a network, and extracts the network address of the printing apparatus from header information of a communication packet.
According to this method, even when the printing apparatus starts using a new network address, the network card device can obtain the network address without making the printing apparatus aware of this. The printing apparatus therefore need to neither determine the type of network card device nor perform any process.
According to this method, however, if the value of a given network address changes to a different one in the printing apparatus, the network card device cannot recognize the change.
Assume that, of network address A and network address B assigned to the printing apparatus, network address A changes to network address C. In this case, the network card device cannot determine whether network address C is newly added or has changed from network address A.
As one means for solving these problems, the printing apparatus obtains or generates a network address, and the network card device inquires the network address of the printing apparatus by a predetermined method, as needed. An inquiry method can, e.g., be a method using MIB (Management Information Base). The printing apparatus has the MIB agent function, and the network card device has the MIB client function.
The network card device inquires network address information of the MIB agent of the printing apparatus, and uses all obtained network addresses as network addresses of the network card device. This method obviates the need for the printing apparatus to determine the type of network card device and perform any process. Even when the value of a given network address changes in the printing apparatus, the network card device can recognize the change.
However, even this method suffers new problems as follows.
As described above, a network address may always be added or changed in the IPv6 protocol. When the above-mentioned means is employed, the network card device must always keep inquiring network address information of the printing apparatus every predetermined period during activation.
More specifically, the network card device obtains all network addresses by an inquiry means such as MIB from the printing apparatus every predetermined period, and determines whether the network addresses have not changed from previously obtained information. If the network card device determines that the network addresses have changed, it sets new address information as network addresses of the network card device itself. The network card device must repeat this process.
Repetitive execution of this process during activation imposes a heavy work burden on both the network card device and the printing apparatus. In an environment where address settings do not so frequently change, most inquires are unnecessary and redundant in many cases.